So Monoprice has an actual tube amp now...

[Dandy]

So you had the unit in your possession but didn't bother to test to see if the tubes actually were doing something. And yet you can definitively tell us It is a "deceptive" piece of junk. Okay! Nice review!

I suspect he opened it up and saw that it was actually a solid state amp and that the tubes were not supplying the power, whether in PP or SE configuration. If advertised as a tube amp that sounds like misleading marketing to me.

 

[shelly_d]

In fairness, all the ads I have seen for that old one did state it was a hybrid.

To am earlier point about how to get 25 watts from an EL84, I have a rebadged Pioneer SM-83 that puts out 27 watts/channel. The original compliment was 7189A's. I am now using EL84M's, which have supposedly been built to the same standards as the 7189. Using those, you can get that kind of power and it is not a lie to state that the outputs are EL84's. Having said that, I am NOT suggesting the amp under discussion produces that, I did see the 10 watts/channel spec as well, I am just pointing out that there are EL84 types now out there that can do that.

Shelly_D

 

[mmickk]

Maybe I am looking at the wrong unit. For their new non-hybrid amp I see it listed has having 4 EL84 for the amp section and rated at 10 watts /channel. I would like to hear from someone who has tried it as well but rather doubt that when I am ready to spend for a tube amp that this would be the one I choose.

And to be clear, as Shelly_d mentioned, on their site both the 25 and 50 watt units are clearly identified as hybrid units even thought they appear in the tube amp section in products.

 

[RamblinE]

Maybe I am looking at the wrong unit. For their new non-hybrid amp I see it listed has having 4 EL84 for the amp section and rated at 10 watts /channel. I would like to hear from someone who has tried it as well but rather doubt that when I am ready to spend for a tube amp that this would be the one I choose.

And to be clear, as Shelly_d mentioned, on their site both the 25 and 50 watt units are clearly identified as hybrid units even thought they appear in the tube amp section in products.

Not to fanboy about the amp I've got but for the money it's pretty legit, and it costs about the same as the Monoprice (before shipping that is, after shipping mine is more). I'm running two Tube Depot 6L6's and two RCA metal bodied 5693's.
http://www.musicalparadise.ca/store/index.php?route=product/product&product_id=54

 

[FlaCharlie]

In fairness, all the ads I have seen for that old one did state it was a hybrid.

To am earlier point about how to get 25 watts from an EL84, I have a rebadged Pioneer SM-83 that puts out 27 watts/channel. The original compliment was 7189A's. I am now using EL84M's, which have supposedly been built to the same standards as the 7189. Using those, you can get that kind of power and it is not a lie to state that the outputs are EL84's. Having said that, I am NOT suggesting the amp under discussion produces that, I did see the 10 watts/channel spec as well, I am just pointing out that there are EL84 types now out there that can do that.

Shelly_D

Just to put things in perspective . . . A typical PP 6BQ5 / EL84 amp will put out 15 wpc. Doubling the power output will get you an extra 3db using the same speakers at the same distance.

So if you're getting 25 wpc, you're getting a whopping 2db more output if you run both amps at maximum volume. Subjectively, that is barely noticeable. If you want to hear what an increase of 2db sounds like, just move 26" closer to your speakers.

I don't know anyone who runs their amps at maximum volume. If you run your amp at more reasonable and typical levels, you would likely not notice any difference at all due to whatever increase in power you get. It takes 10x the power to subjectively double the volume.

I know a lot of people focus on the higher voltage ratings of 7189s and 7189As compared to ordinary 6BQ5s but I contend that the more important spec is plate dissipation. The 6BQ5 is rated for 12w, the 7189, despite the higher voltage limits, is also rated at 12w and the 7189A is rated at 13.2w. Whichever tube you use, if you run the piss out of it, its life will be considerably shortened.

 

[BuzzK]

So you had the unit in your possession but didn't bother to test to see if the tubes actually were doing something. And yet you can definitively tell us It is a "deceptive" piece of junk. Okay! Nice review!

I didn't realize that a complete, empirical "review" was required.

Actually, I did measure voltages and what I measured made no sense.

A "review" by another AKer matched my experience:

"i just picked up my amp from my friend, a talented and careful tech who's done much work for me before. indeed, i had gotten the hum in my left channel by accidentally touching a strand of speaker wire across the outputs. while fixing things up, he discovered that the amp is simply a solid state amp with signal running through the tubes in the preamp first, but with no real contribution from that stage. yes, he says, the amp wont play with no tubes in circuit, but that is because they are really nothing more than attractive fuses. he went on to say that overall, it is nicely constructed, sounds good, but is inaccurately called a 'tube amp'. so now i have a $325, $150 solid state amp i don't really need, with tubes lit up on top."


Go buy one yourself. Knock yourself out.

 

[AdamAnt316]

Sansui claimed that their AU-70 integrated amplifier was capable of 25WPC, using a pair of 7189s in push-pull. Of course, this was back before FTC regulations came about, so they're probably talking in terms of "music power". Here's what the specifications page in the original manual says about the power output section:

And for good measure, what the output section of the AU-70 looks like:

 

[s-petersen]

Likely the Monoprice limitation is the output transformers, I am not sure if the specs refer to 8 ohm, or 4, it does mention the amp is down 2 db at 30HZ. The Sansui has huge output transformers for their power rating, and great specs.

 

[Dandy]

The Monoprice just has 8ohm outputs.

 

[Nixxuz]

I suspect he opened it up and saw that it was actually a solid state amp and that the tubes were not supplying the power, whether in PP or SE configuration. If advertised as a tube amp that sounds like misleading marketing to me.

Hence the use of the term "hybrid". I had one as well. The sound did change after rolling the tubes, but they were explicitly stated as being a buffer preamp section.

 

[Dandy]

Hybrid amps use small signal tubes in the preamp section at the nornal operating voltages. I know because I've built one. I've never used buffer tubes, but my understanding is that they are used at low voltages and are not actually part of the preamp section. But I've not seen one of these 'hybrid' Monoprice offerings. How were the tubes actually used in yours? Got a schematic?

 

[Nixxuz]

Hybrid amps use small signal tubes in the preamp section at the nornal operating voltages. I know because I've built one. I've never used buffer tubes, but my understanding is that they are used at low voltages and are not actually part of the preamp section. But I've not seen one of these 'hybrid' Monoprice offerings. How were the tubes actually used in yours? Got a schematic?

I do not. I'm guessing you could possibly find one out there in the wild, as the model Monoprice slapped their name on was also sold under the Nobsound/Douk/etc. labels. I sold mine fairly fast to finance upgrades later on. Sorry I can't be more help.

 

[Dandy]

No problem. I'm not in the market for one; just curious about them.

 

[Bob]

all hearsay til someone takes a detailed picture of the trace side of the PCB and provides
a matching schematic.

(someone will say "I heard that the monoprice tube amp is a hybrid" and send a ripple
to the next galaxy setting off the real alien invasion)

if its a hybrid, pull the tubes and play it, sound or no sound. think pulling an engine
out of a car.

distortion = 1/2, 1, 2, 3 percent - able to hear the difference or even absolutely?
codify, built instrumentation to match "golden" ears, put business plan together
go IPO, and show on the road to all the high-end shows and salons. charge
thousands for a test, replace the macintosh field labs. save them travel expenses.

me, cant tell .0001% from .1857%, distortion. never bought an amp/preamp/TT/CDP
on specs. did that ONCE. never again. for you spec fanbois it was the zero tracking
angle tonearm of the Garrard Zero-100C, the one turntable that plowed the brand
into the ground. gave it away for free - couldn't afford replacing all those snapped
cantilevers.

as far as distortion goes, didn't Jimi make it to the top with it?

so, play your gear, listen, and enjoy the music.

 

[Nixxuz]

No problem. I'm not in the market for one; just curious about them.

Sorry. Wasn't implying you wanted to buy one. I meant the schematic should be out there, as there were several brands out of China rebranding the same amp.

 

[nbarber]

I purchased one of the Hybrid 25watt tube amps last year. The build quality was consistent with my expectation for $100 amp, ie not great, the Bluetooth was unstable and noting about the unit had any real quality to it. It sounded ok but developed a crackle in the left channel within a couple weeks. I returned it for a refund and most likely won't buy another Monoprice tube amp. From my experience it seems much better equipment is probably available for comparable money.

 

[invaderzim]

Maybe I am looking at the wrong unit. For their new non-hybrid amp I see it listed has having 4 EL84 for the amp section and rated at 10 watts /channel. I would like to hear from someone who has tried it as well but rather doubt that when I am ready to spend for a tube amp that this would be the one I choose.

And to be clear, as Shelly_d mentioned, on their site both the 25 and 50 watt units are clearly identified as hybrid units even thought they appear in the tube amp section in products.

It does seem like the amps being talked about are a variety of different ones that they sell and not just the newer 'tube only' amp that the thread headline is about:
https://www.monoprice.com/product?c_id=109&cp_id=10919&cs_id=1091903&p_id=27222&seq=1&format=2

"The Monoprice Pure Tube Amplifier utilizes four EL84 tubes for the power output stage and three 6N3 tubes for the preamplifier stage to deliver that rich, full-bodied tube sound. This is no hybrid, with a solid state power amplifier stage here! This is a full-blown, all tube amplifier."

Full Specs
Model 27222
Frequency Response 20Hz ~ 20kHz ±2dB
Total Harmonic Distortion 1%
RMS Power Output (4-ohm load @1kHz) 10 watts/channel
Output Impedance Range 4 ~ 8 ohms
Input Impedance 47 kilohms
Input Sensitivity 450mV
Signal-to-Noise Ratio ≥85dB
Input Voltages 100 ~ 120 VAC, 60 Hz / 200 ~ 230 VAC, 50 Hz
Fuse Ratings F2AL/125V
Tube Types EL84 and 6N3
Bluetooth® Version 4.0 with Qualcomm® aptX™ audio codec
Bluetooth Range Up to 32 feet (10 meters)
Dimensions 10.7" x 12.4" x 5.9" (272 x 315 x 150 mm)
Weight 16.1 lbs (7.3 kg)

 

[Dandy]

True, but there is a related issue about the build and sound quality of this low priced all tube amp. Does anyone reading this thread have one to report on?

 

[Nixxuz]

True, but there is a related issue about the build and sound quality of this low priced all tube amp. Does anyone reading this thread have one to report on?

I don't, but I also don't think the quality issue is really related due to the fact that Monoprice just slaps their name on Chinese units. They didn't have anything to do with the design or manufacture of the "hybrid" amps, and I'm sure they don't have anything to do with these, as far as that goes. They just sell them to a mostly Western consumer base at, or around, the price of the ChiFi units if you add in shipping. It may be a possibly good design I suppose, though I doubt the component parts are going to be top notch. I think these units just started selling no more than a month ago.

 

[Walter R]

I bought one to use with my computer. I’ve been ripping LPs and wanted a simple system to monitor the computer audio while ripping without powering up my big McIntosh system. It only cost $139, on both Amazon and eBay, and I already had a pair of old (pretty crappy) speakers. It sounds surprisingly good. It’s a good value for someone on a tight budget.

BTW, the manual says THD < 0.1%, not 1%, but doesn’t say over what frequency range.